This invention relates, in general, to communication system architectures and is particularly, but not exclusively, applicable to an apparatus and method of signalling and management within an exchange environment. The present invention is more specifically directed towards integrating signalling and management in a sub-net of telephony exchanges interconnected through a broadband network such that the sub-net of exchange nodes appears as a single node from a perspective of other external exchanges and management systems. The underlying inventive principle is designed to support migration from existing narrowband telecommunication infrastructure into a broadband domain.
Telecommunication systems are presently undergoing a transition from first generation narrowband digital networks and future multi-media digital networks having broadband capabilities. This transition is necessarily required to support higher data rate communications, including video and Internet applications, that are presently being both considered and made available. Unfortunately, this transitional phase also presents system operators with several dilemmas, and also prejudices immediate implementation of such broadband systems. For example, until such a time when a free-standing broadband system becomes an accepted and freely available standard for all subscriber terminals (such as cellular telephones and data transmission devices), system operators are reticent to write-off their significant investments in current narrowband infrastructure technology. Indeed, such narrowband infrastructure technology already provides a rich set of services and service creation environments that would have to be re-implemented to be deployed in broadband networks.
Consequently, present-day narrowband systems must be adapted to accommodate both narrowband and broadband users; with this statement particularly relevant to call establishment and interworking procedures between these different forms of network.
For an effective migration between narrowband and broadband systems (for the transitional phase), system operators must particularly consider an interworking scenario when all subscribers connect to a narrowband network, but one or more intermediate broadband networks are used to relay information between these narrowband subscribers.
In more detail, telecommunication networks comprise nodes connected by communication resources (usually termed xe2x80x9clinksxe2x80x9d), with a particular network technology characterised by the means of transmission of user and control information along these links and also by the routing and relaying functions embodied in the nodes. The term routing is used to describe the process of determining the path the information will take through the network, while relaying is the process of transferring information from one link to another, i.e. the information is merely passed, without alteration, from one channel resource to another.
In relation to an exemplary narrowband digital network, user and control information (or xe2x80x9cdataxe2x80x9d) is interleaved, using time division multiplexing (TDM), on a 52 kbit per second (kbps) pulse code modulated (PCM) bearer channel. Such bearer channels can each be framed to support four voice calls of 16 kbps, comprised from 13 kbps of sampled and encoded speech and 3 kbit/s of ancillary information, such as parity check and correction bits (and the like) and synchronisation information. Data is then relayed across a node by some form of synchronous TDM switching fabric, often of the xe2x80x98time-space-timexe2x80x99 type. Control information (e.g. call set up and tear down messages) logically follows the same path (although not always the same physical path) through the network as user information, and is terminated in each node for routing purposes. Routing is conventionally performed, in each node, on a xe2x80x98hop-by-hopxe2x80x99 basis using long lived routing tables, i.e. the node is sufficiently intelligent to determine an optimum route for the succeeding network connection.
Control information is regulated by a signalling scheme that is distinctive to the type of network employed. Particularly, public signalling systems are used between nodes of a public network and between public networks of different operators. Signalling System No. 7 is the only important example of a public signalling system. Access signalling systems are used between subscribers and edge nodes of public networks, e.g. between a radiotelephone and a base station subsystem (BSS). In fact, the most common digital access signalling schemes are Common Channel Signalling Systems, such as the Integrated Service Digital Network (ISDN) DSSS1 signalling schemes (and its predecessors) and Channel Associated Signalling schemes that are both derived from analog signalling. Private schemes are generally derived from access schemes but provide richer functionality within personal networks, such as within a secure private branch exchange (PBX).
Broadband digital networks are characterised in that user and control information is transmitted in fixed or variable length xe2x80x98packetsxe2x80x99, with these packets prepended with headers that contain bearer channel identification. In contrast with narrowband systems, user information is relayed across a node via an asynchronous switching fabric that examines each packet in turn (using some kind of fairness algorithm) and directs it to the appropriate output link in response to the input link and bearer channel identification. Routing and control information transmission is, however, similar to that for the narrowband case, and differs only inasmuch as the signalling schemes are technology specific.
As a very brief summary of the general teaching underlying PCT/GB98/0245 (that provides for the interconnection of narrowband and broadband networks), a communication system has a broadband network and a plurality of narrowband exchanges each containing at least one communication device. The narrowband exchanges has differing signalling protocols to those of the broadband network. The narrowband exchanges are interconnected through the broadband network, and the communication system is arranged to establish a communication connection between a calling communication device in a first narrowband exchange and a receiving communication device in a different narrowband exchange. Each of the at least one communication devices has an address. Each of the plurality of narrowband exchanges comprises a call server responsive to a call request message generated by the calling communication device, wherein the call request message contains the address of the calling communication device and a destination address associated with the receiving communication device. The call server is arranged to identify a circuit identity associated with a first communication circuit used to send the call request message to the call server. The narrowband exchanges further include means for selecting a phantom trunk different to the first communication circuit, wherein the phantom trunk has a circuit identity and is arranged to support a narrowband communication between the first narrowband exchange and the different narrowband exchange over the broadband network. Each narrowband exchange further includes: means for sending, in a first message, the destination address and the circuit identity from the first narrowband exchange to the second narrowband exchange; means for sending, in a second message, the circuit identity and the address of the calling communication device to the second narrowband exchange; means for identifying the presence of the circuit identity in both the first message and the second message to establish that the communication connection is between the calling communication device and receiving communication device; and means for establishing the communication connection through the broadband network.
In operation, the call server in a first narrowband exchange, in response to a call from a first subscriber terminal to a second subscriber terminal in the different narrowband exchange, selects a phantom trunk between the two exchanges. The phantom trunk has a unique circuit identity, which circuit identity is used in a first instance to relay to the second (i.e. different) exchange an address of the second subscriber terminal. Then, in a second instance, the unique circuit identity is used to relay to the second exchange an address of the first subscriber terminal. By recognising that two connection requests have been received at opposite ends of the same phantom trunk, a processor in the second exchange is able to determine that a direct connection between the first and second subscriber terminals is required through the broadband network.
In relation to the interconnection of exchange-related infrastructure, such as switches and narrowband-broadband interworking devices (referred to as xe2x80x9cmulti-service platformsxe2x80x9d or xe2x80x9cMSPsxe2x80x9d), whilst it is preferably to have a distributed system in which catastrophic system failure can be avoided by the re-routing of traffic through physically separate but equivalent functional entities (in addition to built-in redundancy provisions), system operators prefer to operate and manage a unitary system from both an operations perspective and a signalling perspective. The principal reason behind the requirement of a unitary system is that management and call handling is simplified, and adaptation of the system is relatively easy in that a change in configuration is achievable from a single entry point.
In view of development time, cost and complexity of exchange-related infrastructure, it is fundamentally essential that migration from existing narrowband systems to fully-fledged and independent broadband systems takes place, as previously indicated. In this regard, narrowband architectures such as the DMS(trademark) exchange manufactured by Northern Telecom Limited, provide a foundation for mixed and, ultimately, solely broadband-based systems. In fact, the DMS(trademark) exchange now provides a full set of call processing and routing features by virtue of its development over many years, with the DMS(trademark) exchange supported by many millions of lines of program code.
Network operators are continually demanding higher performance from exchanges by virtue of generally increasing levels of traffic, both in terms of the number of calls/connections and the capacity (and hence the bandwidth) assigned to each call/connection. However, exchanges are already reaching their optimum size (in terms of processing capabilities). For example, a call server that invokes feature codes and also oversees the set-up of circuit-to-circuit (in a narrowband sense) and circuit-to-virtual path connections across a broadband interface only has a limited processing capability and can only support a limited number of peripheral entities and connections. Of course, the call server can be upgraded, but such up-grades are generally a temporary fix and require supplementary equipment that itself eventually presents access, interconnection, heating and encapsulation (in the sense of overall size) problems. Indeed, the call server of the DMS(trademark) exchange has been undergone upgrades to what is now termed an XA-core(trademark), but the processing capacity of the single XA-core(trademark) is nevertheless restricted to supporting a finite number of peripherals, such as information servers and broadband routing devices. Such peripherals generally support additional traffic capacity.
In relation to present handling capacity, exchanges typically handle less than about one million busy hour call (BHCA) attempts, but network operators are already stipulating a requirement for systems that have a capability of handling five million BHCA (and more). There is clearly a vast discrepancy in these two figures, with the difference unfortunately not immediately reconcilable through existing system design.
Network operators are therefore clearly desirous of the development of communication systems that provide increased processing capabilities whilst presenting a uniform view and single-entry point with respect to both an operations perspective and a signalling perspective.
According to a first aspect of the present invention there is provided a communication system comprising: a plurality of multi-service hubs (MSH), each MSH comprising an exchange having at least one multi-service platform (MSP), the exchange and the at least one MSP managed by an element manager that co-ordinates management thereof; an operations and support system (OSS) providing a control interface to an operator of the communication system; and an intermediate element manager coupled to each element manager in each MSH, the intermediate element manager further coupled to the OSS and configured to intercept system management information passed between the OSS and each of the element managers such that the intermediate element manager provides a single address point to the OSS while also appearing to be an OSS to each element manager in each MSH.
In a second aspect of the present invention there is provided a method of managing a communication system comprising a plurality of multi-service hubs (MSH) each having an exchange with at least one multi-service platform (MSP), the exchange and the at least one MSP managed by an element manager that co-ordinates management thereof, the communication system further comprising an operations and support system (OSS) providing a control interface to an operator of the communication system and an intermediate element manager interconnecting each element manager in each MSH and the OSS, the method comprising the steps of: restricting a passage of system management information between the OSS and selected ones of the plurality of element managers to a path via the intermediate network manager, such that the intermediate element manager provides a single address point to the OSS while also appearing to be an OSS to each element manager in each MSH
Preferably, the intermediate element manager comprises a memory containing a connection map, and the method further comprising the steps of: stripping-out system addressing incident to the intermediate element manager from the OSS; and routing system management information to individual MSHs through use of the connection map.
In the intermediate element manager, it is preferred that the method further include the step of consolidating information from each element manager in each MSH to the OSS, thereby to ensure that the OSS receives system management information from a single node only.
In a preferred embodiment, each of the plurality of MSHs contains an associated call server, and the method of consolidating acts to consolidate, onto a single flow, at least one of: log records from call servers and MSPs; and performance measures from the call servers and MSPs, said the performance measures typically reflecting traffic flows and semi-permanent virtual channel set-up rates.
The step of consolidating may further include the step of identifying affected/failed system entities by at least one of name and location.
The intermediate element manager may also act to queue system management information; and re-package said system management information into blocks of related data.
Furthermore, the intermediate element manager, may act to strip-out superfluous data from messages communicated to it by the each of the element managers.
In another embodiment, the method further comprises the step of: at the intermediate element manager, merging billing streams emanating from each MSH (314-322) to produce a network billing record.
The method may also include the step, at the intermediate element manager, of correlating billing records from a plurality of call managers involved in a call across the communication system, thereby providing a single consolidated record for each call.
In a further aspect of the present invention there is provided a communication system comprising a plurality of logical exchanges each assigned a unique address point code, at least one of said logical exchanges being a sub-network containing a plurality of multi-service hubs interconnectable to one another through a broadband domain, each multi-service hub further coupled through communication resources to at least one of the remaining logical exchanges, each multi-service hub further being uniquely assigned a hidden point code different to any of the address point codes assigned to the logical exchanges, and wherein the hidden point codes: support interconnection of a first MSH to a second MSH through the broadband domain; and are inaccessible from a connection perspective from outside the sub-network.
The hidden point codes may be used to support management information, but are generally only used within the sub-network.
The communication system preferably further comprises means for converting between an address point code and a hidden point code.
The means for converting, which is coupled to the remaining logical exchanges, translates a first address point code of the sub-network into a first hidden point code associated with an MSH entry point into the sub-network and further translates a second hidden point code associated with an MSH exit point from the sub-network into the address point code in onward routing of signalling messages to a destination address associated with one of said remaining logical exchanges.
In a preferred embodiment, said means for converting comprises: a signal transfer point (STP) providing a signal routing function and accessible by the plurality of logical exchanges; and a signalling server 352 coupled to the STP, the signalling server further coupled to the broadband domain and arranged to logically interconnect each MSH and to provide a sub-network routing function for interworking on an intra-MSH basis.
In a particular embodiment, each multi-service hub is assigned at least one unique hidden point code different to any of the address point codes assigned to the logical exchanges.
The signalling server) typically has an associated memory that contains a point code mapping function between address point codes and hidden point codes. The functionality of the STP may be collocated with the signalling server.
In yet another aspect of the present invention there is provided a method of establishing a connection across an intermediate sub-network containing a plurality of multi-service hubs (interconnectable to one another through a broadband domain, each multi-service hub further coupled through communication resources to at least one logical exchange external to the sub-network, the method comprising the steps of: assigning individual address point codes to each logical exchange external to the sub-network and also to the sub-network; and uniquely assigning at least one hidden point code different to any of the address point codes assigned to the logical exchanges, to each multiservice hub, and wherein the hidden point codes are inaccessible from a connection perspective from outside the sub-network.
In a preferred embodiment, the method of establishing a connection across an intermediate sub-network further comprises the steps of: establishing a connection between a first logical exchange having a first address point code and a second logical exchange having a second address point code via a first MSH having a first hidden point code, a second MSH having a second hidden point code and the broadband domain, the step of establishing further comprising the step of: and converting between an address point code and a hidden point code upon entry into and exit from the sub-network.
In a preferred embodiment, the step of establishing further comprises the steps of: translating the address point code of the sub-network into the first hidden point code associated with an MSH entry point into the sub-network; and translating the second hidden point code associated with an MSH exit point from the sub-network into the second address point code associated with a destination address of the second logical exchange.
Most preferably, the method further comprising the steps of: providing a database that cross-references hidden point codes and point codes addresses; obtaining an indication of the MSH exit point from dialled digits emanating from the first logical exchange; determining the second hidden point code from the database; and providing a path between the MSH entry point and the MSH exit point.
In a further aspect of the present invention there is provided an intermediate element manager for a communication system comprising a plurality of multi-service hubs (MSH) each having an exchange with at least one multi-service platform (MSP), the exchange and the at least one MSP managed by an element manager that co-ordinates management thereof, the communication system further comprising an operations and support system (OSS) providing a control interface to an operator of the communication system, wherein: the intermediate element manager is arranged to be coupled to each element manager in each MSH and also to be coupled to the OSS, the intermediate element manager configured to intercept system management information passed between the OSS and each of the element managers such that the intermediate element manager provides a single address point to the OSS while also appearing to be an OSS to each element manager in each MSH and such that the intermediate element manager relays system management information between the OSS to each element manager.
Advantageously, the present invention provides a communication system with a uniform operational and signalling perspective whilst beneficially maintaining a distributed architecture that inherently supports system recovery from individual exchange failures. In other words, the distributed nature of a multi-MSH environment is hidden from a service provider, whilst the system is robust and able to support re-routing should any individual MSH suffers a temporary but fatal system failure. Consequently, an operator is provided with a single node view from the perspective of an operations layer, whilst each exchange perceives the intermediate element manager as a network manager and is therefore beneficially oblivious of other exchanges/MSHs within the communication system. Moreover, the preferred embodiment of the present invention supports a significant increase in system handling capacity whilst maintaining an underlying network architecture of existing narrowband systems. Furthermore, migration to a fully-fledged broadband (access) network is supported through relatively simply modification of system connectivity.
In relation to the term xe2x80x9cMSHxe2x80x9d, this is described in detail in the subsequent text with specific reference being made to FIG. 1 and the typical exchange environment 50.
The improved system can beneficially be offered without having to change or enhance existing DMS(trademark) and MSH security schemes.